Bloating and distention in irritable bowel syndrome: the role of visceral sensation

Functional Abdominal Bloating and Gut Microbiota: An Update

(1) Background: Functional abdominal bloating and distension (FAB/FAD) are common disorders of the gut-brain interaction. Their physiopathology is complex and not completely clarified, although gut microbiota imbalances play a central role. The treatment of FAB/FAD still represents a clinical challenge for both patients and healthcare providers. Gut microbiota modulation strategies might play a crucial role in their management. The aim of this narrative review was to update the current evidence on FAB/FAD, with a focus on gut microbiota. (2) Methods: In October 2023, a review was conducted through the Medline, PubMed, and Embase databases. Selected literature included all available English-edited studies (randomized controlled trials and cross-sectional, cohort, and case-control studies). (3) Results: Twelve studies were selected, most of which investigated the relationship between IBS and microbiota, with bloating being one of its symptoms. The studies suggest that restoring a balanced microbiome appears to be the most promising solution for better management of FAB/FAD. Targeted approaches, such as the use of probiotics, prebiotics, antibiotics such as rifaximin or dietary modifications, may hold the key to alleviating symptoms. Other therapeutic options, such as diet, neuromodulators, and brain-gut behavioral therapies (i.e., cognitive-behavioral therapy) have shown promising outcomes, but strong data are still lacking. (4) Conclusions: Targeted approaches that focus on the gut microbiota, such as the use of probiotics, prebiotics, and antibiotics, are essential in managing FAB/FAD. Understanding the complex relationship between gut microbiota and FAB/FAD is crucial for developing effective treatments. Further studies are needed to explore the specific roles of different microbial populations in patients with FAB/FAD to enhance therapeutic strategies.

Review article: A practical approach to persistent gastrointestinal symptoms in inflammatory bowel disease in remission

BACKGROUND

Persistent gastrointestinal symptoms are prevalent in adult patients with inflammatory bowel disease (IBD), even when endoscopic remission is reached. These symptoms can have profound negative effects on the quality of life of affected patients and can be difficult to treat. They may be caused by IBD-related complications or comorbid disorders, but they can also be explained by irritable bowel syndrome (IBS)-like symptoms.

AIMS

To provide a practical step-by-step guide to diagnose and treat persistent gastrointestinal symptoms in patients with IBD in remission via a personalised approach.

METHODS

We scrutinised relevant literature on causes, diagnostics and treatment of persistent gastrointestinal symptoms (abdominal pain or discomfort, bloating, abdominal distension, diarrhoea, constipation and faecal incontinence) in patients with IBD in remission.

RESULTS

A graphical practical guide for several steps in diagnosing, identifying potential triggers and adequate treatment of persistent gastrointestinal symptoms in IBD in remission is provided based on supporting literature. The first part of this review focuses on the diagnostic and treatment approaches for potential IBD-related complications and comorbidities. The second part describes the approach to IBS-like symptoms in IBD in remission.

CONCLUSIONS

Persistent gastrointestinal symptoms in IBD in remission can be traced back to potential pathophysiological mechanisms in individual patients and can be treated adequately. For both IBD-related complications and comorbidities and IBS-like symptoms in IBD in remission, pharmacological, dietary, lifestyle or psychological treatments can be effective. A systematic and personalised approach is required to reduce the burden for patients, healthcare systems, and society.

Efficacy and Safety of Pea Protein and Xyloglucan Versus Simethicone in Functional Abdominal Bloating and Distension

BACKGROUND

Functional Abdominal Bloating and Distension (FABD) is a multifaceted condition related in part to trapped gas, with changes in the intestinal barrier and small intestinal bacterial overgrowth (SIBO), which lead to gas production. Currently, there are no treatments targeting the etiology of FABD.

METHODS

This double-blind, multicenter, randomized study evaluated the safety and efficacy of a product containing xyloglucan and pea proteins (XG + PP) compared with simethicone, both administered orally (three times daily) for 20 consecutive days. Eighty-eight patients with FABD were randomly assigned to the two groups in a 1:1 ratio. Primary outcome was safety; secondary outcomes were (i) efficacy in alleviating the symptoms of FABD and (ii) efficacy in reducing SIBO, as assessed by hydrogen breath test (HBT).

RESULTS

No Adverse Events or Serious Unexpected Adverse Reactions were reported during the study. XG + PP showed a faster onset of action and a significant reduction in bloating and abdominal pain compared with simethicone. At Day 20, XG + PP drastically reduced abdominal girth when compared with simethicone, with an average reduction of 4.7 cm versus 1.8 cm. At Day 20, the XG + PP arm showed a significant reduction in HBT compared to baseline.

CONCLUSIONS

This study supports the evidence that FABD patients may benefit from a XG + PP-based treatment that acts on etiology and not just the symptoms.

Colonic mucosal eosinophilia and immunohistochemical expression of COX-2 and NF-kB in patients with irritable bowel syndrome

BACKGROUND

There is growing evidence that eosinophilic infiltration can release mediators which are harmful to the intestinal epithelium in patients with irritable bowel syndrome (IBS). Although cyclooxygenase 2 (COX-2) and nuclear factor-kappa beta (NF-kB) expression had been previously reported to increase in many inflammatory conditions, there is a paucity in data investigating their expressions in IBS. Our aim was to evaluate colonic mucosal eosinophilia and immunohistochemical expression of COX-2 and NF-kB in patients with irritable bowel syndrome.

METHODS

A total of 80 patients who met the inclusion criteria of IBS based on Rome IV symptoms questionnaire were subjected to abdominal ultrasound, laboratory investigations, serum immunoglobulin E (IgE) level assessment and colonoscopic examination. Immunohistochemistry was performed to detect COX-2 and NF-kB expression in colonic biopsies obtained from IBS patients.

RESULTS

Histopathological examination showed that 60 colonic biopsy specimens (75%) showed few mixed inflammatory cells ≤3 cells/ HPF, 12 biopsy specimens (15%) showed eosinophilic infiltration ≥25 eosinophils/HPF and 8 biopsy specimens (10%) showed severe lymphocytic infiltration and aggregation. Colonic eosinophilic infiltrate was significantly higher among patients presented with IBS-D subtype. Serum IgE was significantly higher among patients with colonic eosinophilic infiltrate than the others. In IBS-D patients, colonic mucosa showed positive expression of COX-2 and NF-kB in 52.1% and 81.25% of cases, respectively.

CONCLUSION

Patients with IBS -particularly IBS-D subtype- should undergo colonoscopy and biopsy to exclude underlying inflammatory pathology. Moreover, patients with positive COX-2 and NF-kB need further evaluation and follow-up.

Improvement in constipation and diarrhea is associated with improved abdominal pain in patients with functional bowel disorders

BACKGROUND

Abdominal pain is a bothersome and lifestyle limiting symptom in patients with functional bowel disorders. It is associated with decreased quality of life in affected individuals, as well as significant annual healthcare expenditure. Knowledge of specific factors that predict improvement in abdominal pain in those with functional bowel disorders is thus far limited.

METHODS

Consecutive patients presenting for outpatient care at a major academic medical center between October 2017 and March 2020 completed an electronic symptom survey prior to initial clinic visit, and again after 3 months. The Rome IV questionnaires for functional dyspepsia, irritable bowel syndrome, functional constipation, and functional diarrhea were all included. Additionally, all subjects completed the Patient Reported Outcomes Measurement Information System Anxiety, Depression, and sleep disturbance questionnaires. Patients with a diagnosis of a Rome IV functional gastrointestinal disorder without any organic cause for symptoms were identified based on both chart review as well as survey response data. Univariable and multivariable analysis was used to assess predictors of improved abdominal pain after 3 months.

KEY RESULTS

180 patients with a mean age of 45.3 years were included in the final analysis. 78.3% of patients were female, and 77.2% met Rome IV criteria for irritable bowel syndrome. On multivariable analysis, improvement in constipation and diarrhea were both independent predictors of improved abdominal pain after 3 months.

CONCLUSIONS AND INFERENCES

Improvement in constipation and diarrhea both predicted improvement in abdominal pain, suggesting that addressing these factors is central to the management of abdominal pain in functional gastrointestinal disorders.

Barostat or syringe-assisted sensory biofeedback training for constipation with rectal hyposensitivity: A randomized controlled trial

BACKGROUND

Rectal hyposensitivity (RH) is a well-known pathophysiological dysfunction in chronic constipation. Whether biofeedback training improves RH and restores bowel function is unknown.

AIM

To investigate the efficacy of barostat-assisted sensory training (BAST) with syringe-assisted sensory training (SAST) in patients with RH in a randomized controlled trial.

METHODS

Patients with RH and chronic constipation (Rome III) were randomized to receive 6 biweekly sessions of BAST or SAST. Verbal/visual feedback was provided during repeated rectal distensions to improve defecation desire/urge and first sensations with either 10-cm balloon connected to barostat (BAST) or 4-cm balloon connected to syringe and manometry probe (SAST). Sensory thresholds, bowel symptoms, and therapist and patient's rating of treatments were compared. The primary outcome (responders) was the improvement in ≥2 sensory thresholds.

RESULTS

Sixty-six patients were enrolled: 32 received BAST, 34 received SAST, and 56 completed study. There were significantly more responders in BAST group than SAST (78% vs. 53%, p = 0.0320). Rectal sensation normalized in 81% with BAST compared to 56% with SAST (p = 0.0270). When compared to baseline, desire and urge to defecate thresholds and bowel satisfaction improved with BAST (p = 0.0013; p = 0.0002; p = 0.0001) and SAST (p = 0.0012; p = 0.0001; p < 0.0001) and number of complete spontaneous bowel movements with BAST (p = 0.0029) but without inter-group differences. Therapists rated BAST as superior to SAST (p < 0.0001), but patients rated both equally.

CONCLUSIONS

Sensory biofeedback training was effective and significantly improved rectal sensation and constipation symptoms. Although both techniques were useful, the novel BAST was more efficacious and easier to administer for treating RH.

British Society of Gastroenterology guidelines on the management of irritable bowel syndrome

Irritable bowel syndrome (IBS) remains one of the most common gastrointestinal disorders seen by clinicians in both primary and secondary care. Since publication of the last British Society of Gastroenterology (BSG) guideline in 2007, substantial advances have been made in understanding its complex pathophysiology, resulting in its re-classification as a disorder of gut-brain interaction, rather than a functional gastrointestinal disorder. Moreover, there has been a considerable amount of new evidence published concerning the diagnosis, investigation and management of IBS. The primary aim of this guideline, commissioned by the BSG, is to review and summarise the current evidence to inform and guide clinical practice, by providing a practical framework for evidence-based management of patients. One of the strengths of this guideline is that the recommendations for treatment are based on evidence derived from a comprehensive search of the medical literature, which was used to inform an update of a series of trial-based and network meta-analyses assessing the efficacy of dietary, pharmacological and psychological therapies in treating IBS. Specific recommendations have been made according to the Grading of Recommendations Assessment, Development and Evaluation system, summarising both the strength of the recommendations and the overall quality of evidence. Finally, this guideline identifies novel treatments that are in development, as well as highlighting areas of unmet need for future research.

Systematic review and network meta-analysis: efficacy of licensed drugs for abdominal bloating in irritable bowel syndrome with constipation

BACKGROUND

Although bloating is a highly prevalent and troublesome symptom in irritable bowel syndrome with constipation (IBS-C), treatment is empirical with no specific guidelines for its management.

AIM

To conduct a pairwise and network meta-analysis, using a frequentist approach, of Food and Drug Administration-licensed drugs for IBS-C comparing their efficacy for abdominal bloating as a specific endpoint.

METHODS

We searched the medical literature through December 2020 to identify randomised controlled trials (RCTs) in IBS-C, with abdominal bloating reported as a dichotomous assessment. Efficacy of each drug was reported as a pooled relative risk (RR) with 95% confidence intervals (CIs) to summarise effect of each comparison tested. Treatments were ranked according to their P-score.

RESULTS

We identified 13 eligible RCTs, containing 10 091 patients. Linaclotide 290 µg o.d., lubiprostone 8 µg b.d., tenapanor 50 mg b.d. and tegaserod 6 mg b.d. were all superior to placebo for abdominal bloating in patients with IBS-C, in both pairwise and the network meta-analyses. Linaclotide demonstrated the greatest improvement in abdominal bloating in both pairwise and network meta-analysis (RR of failure to achieve an improvement in abdominal bloating = 0.78; 95% CI 0.74-0.83, number needed to treat = 7, P-score 0.97). Indirect comparison revealed no significant differences between individual drugs.

CONCLUSIONS

We found all licensed drugs for IBS-C to be superior to placebo for abdominal bloating. Linaclotide appeared to be the most efficacious at relieving abdominal bloating. Further research is needed to assess long-term efficacy of these agents and to better understand the precise mechanism of improving bloating.

Chronic constipation in adults: Contemporary perspectives and clinical challenges. 1: Epidemiology, diagnosis, clinical associations, pathophysiology and investigation

BACKGROUND

Chronic constipation is a prevalent disorder that affects patients' quality of life and consumes resources in healthcare systems worldwide. In clinical practice, it is still considered a challenge as clinicians frequently are unsure as to which treatments to use and when. Over a decade ago, a Neurogastroenterology & Motility journal supplement devoted to the investigation and management of constipation was published (2009; 21 (Suppl.2)). This included seven articles, disseminating all themes covered during a preceding 2-day meeting held in London, entitled "Current perspectives in chronic constipation: a scientific and clinical symposium." In October 2018, the 3rd London Masterclass, entitled "Contemporary management of constipation" was held, again over 2 days. All faculty members were invited to author two new review articles, which represent a collective synthesis of talks presented and discussions held during this meeting.

PURPOSE

This article represents the first of these reviews, addressing epidemiology, diagnosis, clinical associations, pathophysiology, and investigation. Clearly, not all aspects of the condition can be covered in adequate detail; hence, there is a focus on particular "hot topics" and themes that are of contemporary interest. The second review addresses management of chronic constipation, covering behavioral, conservative, medical, and surgical therapies.

Clinical Impact of Rectal Hyposensitivity: A Cross-Sectional Study of 2,876 Patients With Refractory Functional Constipation

INTRODUCTION

Normal bowel function requires intact sensory pathways. Diminished rectal sensation (rectal hyposensitivity [RH]) is associated with constipation, although its clinical importance remains unclear.

METHODS

Consecutive patients (aged 18-80) attending a tertiary center (2004-2016) for investigation of refractory functional constipation (Rome IV core criteria defined, applied post hoc) were included. Patients completed a clinical symptom questionnaire and underwent anorectal physiologic investigations, including rectal sensory testing (balloon distension) to determine 3 well-established sensory thresholds. Multivariate regression analyses were performed to evaluate associations between RH, symptomology, and allied physiologic investigations.

RESULTS

Of 2,876 patients meeting inclusion criteria, 722 (25%) had RH based on ≥1 elevated sensory thresholds (0: n = 2,154 [74.9%]; 1: n = 327 [11.4%]; 2: n = 209 [7.3%]; and 3: n = 186 [6.5%]). A linear relationship existed between increasing number of elevated sensory thresholds and constipation severity (Cleveland Clinic constipation score: mean difference per threshold [95% confidence interval] 0.69 [0.48-0.90]; P < 0.001). Several symptoms were significantly (P < 0.05) associated with RH including: infrequent defecation (odds ratio 1.29 [1.17-1.42]), painful evacuation (1.15 [1.05-1.27]), prolonged toileting (1.14 [1.05-1.24]), and digitation or enema use (1.18 [1.08-1.30]). On defecography, a "functional" evacuation disorder was also associated with RH (1.37 [1.25-1.50], P < 0.001), as was megarectum (2.52 [2.08-3.05], P < 0.001).

DISCUSSION

RH occurs in 25% of patients with refractory functional constipation. Increased number of elevated sensory thresholds is associated with more severe constipation phenotype. These data, in the largest study to date, provide for the first time evidence to show that RH is a major pathophysiologic mechanism in constipation, with recognized clinical impact (http://links.lww.com/AJG/B765).(Equation is included in full-text article.).

Management of Chronic Abdominal Distension and Bloating

Abdominal bloating and distension are 2 of the most commonly reported gastrointestinal symptoms. Abdominal bloating is characterized by symptoms of trapped gas, abdominal pressure, and fullness. Abdominal distension is defined as a measurable increase in abdominal girth. These symptoms frequently co-exist, although they can occur separately. Defined by Rome IV criteria, functional abdominal bloating and distension commonly coincide with other functional gastrointestinal disorders, such as functional dyspepsia, irritable bowel syndrome, and functional constipation. Abdominal bloating and distension can develop for multiple reasons, including food intolerances, a previous infection that perturbed the intestinal microbiota, disordered visceral sensation, delayed intestinal transit, or an abnormal viscero-somatic reflux. Treatment can be challenging to patients and providers-no regimen has been consistently successful. Successful treatment involves identifying the etiology, assessing severity, educating and reassuring patients, and setting expectations. Therapeutic options include dietary changes, probiotics, antibiotics, prokinetic agents, antispasmodics, neuromodulators, and biofeedback. We review the epidemiology and effects of chronic bloating and distension and pathophysiology, discuss appropriate diagnostic strategies, and assess available treatment options.

How much bloating in the irritable bowel syndrome?

The irritable bowel syndrome (IBS) is the most common chronic gastrointestinal disorder referred to gastroenterologists. One of the most common manifestations of IBS is bloating. Abdominal bloating is defined as subjective sensation of abdominal distension associated with girth increment. Therefore, it is described in the Rome IV criteria as bloating/abdominal distension. Bloating symptoms are reported by 10-30% of the general population and it was rated as the most bothersome symptom by 60% of IBS patients; the lack of specificity of this complaint prevented bloating to be included between the diagnostic criteria for IBS. Indeed, bloating may be reported also in healthy people or in other functional conditions. This paper looks to the evolutions of the concepts on bloating according to the Rome working groups from the beginning until now and it represents a comprehensive review on the prevalence and pathogenesis of bloating.

Symptomatic Management of Gastroparesis

Gastroparesis is a chronic and debilitating neuromuscular disorder of the upper gastrointestinal tract. Symptoms of gastroparesis include nausea, vomiting, epigastric pain, early satiety, and weight loss. Treating gastroparesis can be difficult. Dietary changes may improve symptoms in patients with mild disease. A variety of medications can be used to treat symptoms of nausea and vomiting, although most have not been subjected to randomized controlled trials and only one is approved by the Food and Drug Administration (metoclopramide). Pain management is essential, as nearly 90% of patients report symptoms of epigastric pain. This article reviews treatment options for symptoms of gastroparesis.

Functional Dyspepsia and Severity of Psychologic Symptoms Associate With Postprandial Symptoms in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Patients with irritable bowel syndrome (IBS) have an increased response of postprandial symptoms to a combined lactulose nutrient challenge test, compared with healthy volunteers. We investigated the associations among comorbid functional dyspepsia (FD), severity of psychologic symptoms, and breath test results in response to this test.

METHODS

We performed a prospective study of 205 patients with IBS (Rome III criteria), 94 of whom also had FD (IBS-FD), and 83 healthy volunteers in Sweden from 2008 through 2015. All participants completed a breath hydrogen test after a 400-mL liquid meal with 25 g lactulose. Gastrointestinal (GI) symptom severity was assessed using a graded scale and digestive comfort was recorded before the meal and every 15 minutes until 240 minutes after the meal. GI symptom scores over time were compared between groups using linear mixed models with anxiety, depression, and somatization as covariates.

RESULTS

Average levels of all GI symptoms varied over time among all groups (P < .0001). Patients with IBS-FD had higher levels of bloating (P = .004), abdominal pain (P = .005), and lower levels of digestive comfort (P < .01) than patients with only IBS. We observed a difference in increase in abdominal pain from baseline between IBS-FD and IBS groups (P = .013). Anxiety levels were associated with levels of all symptoms (all P < .025) except abdominal pain, which was associated with somatization severity (P < .0001). Furthermore, anxiety levels associated with level of exhaled hydrogen (P = .0042).

CONCLUSIONS

In a prospective study of patients with IBS, we found those with FD to have increased GI symptoms before and after a liquid meal with lactulose. Anxiety and somatization have an independent additional effect. The presence of comorbid FD and levels of psychologic symptoms affect reports of food-related symptoms in patients with IBS. ClinicalTrial.gov no: NCT01252550.

Abdominal distension in health and irritable bowel syndrome: The effect of bladder filling

BACKGROUND & AIMS

Abdominal distension is a common feature of irritable bowel syndrome (IBS), which is difficult to treat and can have the appearance of late pregnancy. It results from an abnormality of the normal accommodation reflex which keeps abdominal girth constant despite changes in gastrointestinal volume resulting from food ingestion or gas accumulation. We speculated that bladder filling might also trigger this abnormal reflex in IBS and this study tested this hypothesis.

METHODS

Eight females with IBS (aged 21-43, mean 34) were compared with seven female controls (aged 19-56, mean 31) at the same time in the menstrual cycle. Abdominal girth in response to maximum tolerated bladder filling following ingestion of 1500 mls of water was measured using abdominal inductance plethysmography. Symptoms, girth change after bladder emptying, and urine volumes were also recorded.

KEY RESULTS

Baseline girth of patients and controls was 84.8 and 79.9 cm respectively. After reaching maximum tolerated bladder filling, girth increased by a mean of 6.4 (Standard deviation (SD) 2.1) cm in patients compared with 3.5 (1.1) in controls (P = 0.006), with patients having symptoms of bladder hypersensitivity. After voiding urine, girth reduced by 5.3 (3.1) and 1.9 (1.2) in patients vs controls (P = 0.018), despite passing similar mean urine volumes, 789 (364) mls vs 671(286) (P = 0.50).

CONCLUSIONS & INFERENCES

Bladder filling contributes to abdominal distension in IBS and is unrelated to urine volume suggesting that bladder stretch or hypersensitivity might trigger this response. Frequent bladder emptying may help control this intrusive problem which is very challenging to manage.

Are characteristics of abdominal pain helpful to identify patients with visceral hypersensitivity in irritable bowel syndrome? Results of a prospective study

BACKGROUND

Some consider that patients with visceral hypersensitivity may represent a separate entity within the IBS population not only from a pathophysiological but also from a clinical perspective. The aim of this prospective exploratory study was to assess whether characteristics of abdominal pain in IBS patients could be suggestive of hypersensitivity.

METHODS

This prospective study included consecutive IBS patients selected by Rome III criteria. Validated scores (IBS-SSS, Bristol stool scale, HADS) were used to phenotype patients who were also asked to describe the main location of their abdominal pain on a simple image (abdomen divided into 6 zones). Progressive isobaric rectal distensions were performed to demonstrate, with the ascending method of limits, allodynia (pain threshold lower than 24 mmHg).

KEY RESULTS

Fifty patients (women: 72%), 42.6 ± 15.7 years old, were included. Sub-types were IBS-D, IBS-C and IBS-M in 58%, 22% and 20% of cases, respectively. Allodynia was present in 18% of cases. Neither IBS-SSS nor intensity of pain was predictive of hypersensitivity. In hypersensitive patients, pain was more often located in one of the two iliac fossa (P = 0.02) and located outside these areas in only 11% of cases. The sensitivity and the specificity of this pain location to differentiate hyper from normosensitive patients were 0.89 and 0.59, respectively.

CONCLUSIONS & INFERENCES

The location of pain is different between hyper and normosensitive IBS patients. Pain located outside one of the two iliac fossa suggests that the patient is normosensitive.

The role of diet in the management of irritable bowel syndrome: a focus on FODMAPs

Irritable bowel syndrome is a common condition that negatively impacts quality of life and results in significant health care expenditures. The vast majority of IBS patients associate their symptoms with eating. Numerous randomized, controlled trials suggest that restriction of dietary FODMAPs improves overall symptoms, abdominal pain, bloating and quality of life in more than half of IBS sufferers. There is emerging data which suggests that other diets (gluten free, guided elimination diets) might also be of benefit to IBS patients. Areas covered: Comprehensive literature review on dietary therapies available for IBS to date and exploration into individualized dietary therapy development based on diagnostic testing. Expert commentary: FODMAP elimination identifies IBS patients who are sensitive to FODMAPs. Responders should undergo a structured reintroduction of foods containing FODMAPs to determine a patient's sensitivities. This information can then be used to create a personalized, less restrictive low FODMAP diet. Future research should focus on the identification of other effective diet therapies focusing on supplementation of functional foods in addition to elimination and the development of biomarker-based diet treatment plans which identify the right treatment for the right patient.

[Bloating]

Bloating is one of the most common and troublesome problems in a large proportion of patients with gastrointestinal disorders but the mechanism is not completely understood. Several factors, including gas-producing intestinal microbiota, disturbed handling of intestinal gas, visceral hypersensitivity, abnormal viscero-somatic responses, fermentable diet, and psychological factors, have been suggested as mechanisms. For an assessment, thorough medical history-taking and physical examination are the first steps. On the other hand, organic disorders should always be considered first for a differential diagnosis. The therapeutic options available are considered challenging and still limited in clinical practice. The treatment strategy may include diet modification, pharmacologic approach, psychiatric approach, biofeedback, etc. Further studies will be needed to explore the variable mechanism of bloating and develop an efficient treatment.

Correction of Abdominal Distention by Biofeedback-Guided Control of Abdominothoracic Muscular Activity in a Randomized, Placebo-Controlled Trial

BACKGROUND & AIMS

Abdominal distention is produced by abnormal somatic postural tone. We developed an original biofeedback technique based on electromyography-guided control of abdominothoracic muscular activity. We performed a randomized, placebo-controlled study to demonstrate the superiority of biofeedback to placebo for the treatment of abdominal distention.

METHODS

At a referral center in Spain, we enrolled consecutive patients with visible abdominal distention who fulfilled the Rome III criteria for functional intestinal disorders (47 women, 1 man; 21-74 years old); 2 patients assigned to the placebo group withdrew and 2 patients assigned to biofeedback were not valid for analysis. Abdominothoracic muscle activity was recorded by electromyography. The patients in the biofeedback group were shown the signal and instructed to control muscle activity, whereas patients in the placebo received no instructions and were given oral simethicone. Each patient underwent 3 sessions over a 10-day period. The primary outcomes were subjective sensation of abdominal distention, measured by graphic rating scales for 10 consecutive days before and after the intervention.

RESULTS

Patients in the biofeedback group effectively learned to reduce intercostal activity (by a mean 45% ± 3%), but not patients in the placebo group (reduced by a mean 5% ± 2%; P < .001). Patients in the biofeedback group learned to increase anterior wall muscle activity (by a mean 101% ± 10%), but not in the placebo group (decreased by a mean 4% ± 2%; P < .001). Biofeedback resulted in a 56% ± 1% reduction of abdominal distention (from a mean score of 4.6 ± 0.2 to 2.0 ± 0.2), whereas patients in the placebo group had a reduction of only 13% ± 8% (from a mean score of 4.7 ± 0.1 to 4.1 ± 0.4) (P < .001).

CONCLUSIONS

In a randomized trial of patients with a functional intestinal disorder, we found that abdominal distention can be effectively corrected by biofeedback-guided control of abdominothoracic muscular activity, compared with placebo. ClincialTrials.gov no: NCT01205100.

Bloating and Abdominal Distension: Old Misconceptions and Current Knowledge

Bloating, as a symptom and abdominal distension, as a sign, are both common functional-type complaints and challenging to manage effectively. Individual patients may weight differently the impact of bloating and distension on their well-being. Complaints may range from chronic highly distressing pain to simply annoying and unfashionable protrusion of the abdomen. To avoid mishaps, organic bloating, and distension should always be considered first and appropriated assessed. Functional bloating and distension often present in association with other manifestations of irritable bowel syndrome or functional dyspepsia and in that context patients tend to regard them as most troublesome. A mechanism-based management bloating and distension should be ideal but elucidating key operational mechanisms in individual patients is not always feasible. Some clues may be gathered through a detailed dietary history, by assessing bowel movement frequency and stool consistency and special imaging technique to measure abdominal shape during episodes of distension. In severe, protracted cases it may be appropriate to refer the patient to a specialized center where motility, visceral sensitivity, and abdominal muscle activity in response to intraluminal stimuli may be measured. Therapeutic resources focussed upon presumed or demonstrated pathogenetic mechanism include dietary modification, microbiome modulation, promoting gas evacuation, attenuating visceral perception, and controlling abdominal wall muscle activity via biofeedback.

The low-FODMAP diet in the management of functional dyspepsia in East and Southeast Asia

Functional dyspepsia (FD) is a common disorder in East and Southeast Asia where subjects experience post prandial fullness/bloating, early satiety, belching, epigastric pain, and/or burning. A subset of patients with FD experience triggers exclusively related to meals, defined as the post prandial distress syndrome in the Rome IV guidelines. There is significant overlap of symptoms and implicated pathogenic factors with another common functional gastrointestinal disorder, irritable bowel syndrome (IBS) and in fact, a significant proportion of subjects have FD/IBS overlap. The introduction of the low-FODMAP diet has changed the paradigm of treatment for IBS. Like IBS, dietary management appears to be important to patients with FD and clinicians treating the condition. This review aims to examine the current role of diet in the management of FD in East and Southeast Asia, with an exploration of the likely efficacy and mechanisms of action of the low-FODMAP diet in this region.

Hippocampal AMPARs involve the central sensitization of rats with irritable bowel syndrome

OBJECTIVE

The roles of hippocampal AMPARs were investigated in irritable bowel syndrome (IBS)-like rats to clarify the central sensitization mechanisms.

METHODS

IBS model was induced by neonatal maternal separation. The effects of AMPARs on visceral hypersensitivity were examined by the responses of abdominal muscle to colorectal distension after the bilateral intrahippocampal injections of CNQX (an AMPAR inhibitor). The expressions of hippocampal AMPARs (GluR1 and GluR2) were determined by Western blot.

RESULTS

The IBS-like rats showed visceral hypersensitivity when compared with controls. Bilateral intrahippocampal injections of CNQX alleviated the visceral pain in IBS-like rats. The maximal effect appeared at the time point of 30 min, and the duration lasted for 90 min after CNQX application, under 40 and 60 mmHg CRD. The expressions of hippocampal GluR2 significantly increased in IBS-like rats when compared with controls (p < .05). However, the levels of hippocampal GluR1 had no significant differences in rats. Hippocampal LTP induced by HFS was significantly enhanced when compared with controls (p < .05). The expressions of GluR2 significantly increased in the control and IBS-like rats after 60 min LTP of recordings (p < .05), but not GluR1.

CONCLUSION

Neonatal maternal separation enhances the expression of GluR2 and facilitates the LTP in the hippocampus, which could lead to the formation of visceral hypersensitivity when grown up.

Irritable bowel syndrome evaluation using computed tomography colonography

AIM

To evaluate the morphology of the colon in patients with irritable bowel syndrome (IBS) by using computed tomography colonography (CTC).

METHODS

Twelve patients with diarrhea type IBS (IBS-D), 13 patients with constipation type IBS (IBS-C), 12 patients with functional constipation (FC) and 14 control patients underwent colonoscopy following CTC. The lengths of the rectosigmoid colon, transverse colon and the total colon were measured. The diameters of the rectum, sigmoid colon, descending colon, transverse colon, and ascending colon were measured.

RESULTS

The mean length of the total colon was 156.5 cm in group C, 158.9 cm in group IBS-D, 172.0 cm in group IBS-C, and 188.8 cm in group FC. The total colon in group FC was significantly longer than that in group C (P < 0.05). The mean length of the rectosigmoid colon was 56.2 cm, 55.9 cm, 63.6cm, and 77.4 cm (NS). The mean length of the transverse colon was 49.9 cm, 43.1 cm, 57.0 cm, and 55.0 cm. The transverse colon in group IBS-D was significantly shorter than that in group IBS-C (P < 0.01) and that in group FC (P = 0.02). The mean diameter of the sigmoid colon was 4.0 cm, 3.3 cm, 4.2 cm, and 4.3 cm (NS). The mean diameter of the descending colon was 3.6 cm, 3.1 cm, 3.8 cm, and 4.3 cm. The descending colon diameter in group IBS-D was significantly less than that in group IBS-C (P = 0.03) and that in group FC (P < 0.001). The descending colon diameter in group FC was significantly greater than that in group C (P = 0.04). The mean diameter of the transverse colon was 4.4 cm, 3.3 cm, 4.2 cm, and 5.0 cm (NS).

CONCLUSION

CT colonography might contribute the clarification of subtypes of IBS.

Dietary Triggers in Irritable Bowel Syndrome: Is There a Role for Gluten?

A tight link exists between dietary factors and irritable bowel syndrome (IBS), one of the most common functional syndromes, characterized by abdominal pain/discomfort, bloating and alternating bowel habits. Amongst the variety of foods potentially evoking "food sensitivity", gluten and other wheat proteins including amylase trypsin inhibitors represent the culprits that recently have drawn the attention of the scientific community. Therefore, a newly emerging condition termed non-celiac gluten sensitivity (NCGS) or nonceliac wheat sensitivity (NCWS) is now well established in the clinical practice. Notably, patients with NCGS/NCWS have symptoms that mimic those present in IBS. The mechanisms by which gluten or other wheat proteins trigger symptoms are poorly understood and the lack of specific biomarkers hampers diagnosis of this condition. The present review aimed at providing an update to physicians and scientists regarding the following main topics: the experimental and clinical evidence on the role of gluten/wheat in IBS; how to diagnose patients with functional symptoms attributable to gluten/wheat sensitivity; the importance of double-blind placebo controlled cross-over trials as confirmatory assays of gluten/wheat sensitivity; and finally, dietary measures for gluten/wheat sensitive patients. The analysis of current evidence proposes that gluten/wheat sensitivity can indeed represent a subset of the broad spectrum of patients with a clinical presentation of IBS.

Utility of wireless motility capsule and lactulose breath testing in the evaluation of patients with chronic functional bloating

BACKGROUND

The precise aetiology of chronic bloating remains poorly understood and underlying gastroparesis, small bowel bacterial overgrowth and colonic inertia may, individually or collectively, play a role.

AIMS

In this retrospective cohort analysis of symptomatic patients with chronic persistent bloating, we determined the clinical utility of wireless motility capsule and lactulose breath test in further defining the underlying aetiology for functional bloating.

METHODS

Consecutive patients with chronic bloating underwent clinical assessment, wireless motility capsule testing and lactulose breath testing using standard protocols.

RESULTS

52 patients qualified for inclusion in this analysis, fulfilling Rome III criteria for functional bloating. Most patients (54%) had an abnormal wireless motility capsule study; of those, 11.5% had evidence of gastroparesis, 7.7% had small bowel transit delay, 15.8% had colonic inertia, 3.8% had delayed gastric and small bowel transit, 5.6% had combined gastric and colonic transit delay, 3.8% had delayed small bowel and colonic transit, and 5.6% had delayed gastric, small bowel and colon transit times. Using clinical questionnaires the median scores for bloating, constipation and eructation were not significantly different. Neither constipation nor eructation was specific to gastroparesis or colonic inertia but bloating was numerically more prevalent and severe in patients with delayed small bowel transit. 40% of patients had positive lactulose breath test but had no distinguishing clinical characteristics.

CONCLUSIONS

Chronic functional bloating may reflect underlying gastroparesis, small intestinal bacterial overgrowth or colonic inertia. Wireless motility capsule and lactulose breath test are useful in the assessment of patients with bloating and should be considered during evaluation.

Phenotyping of subjects for large scale studies on patients with IBS

BACKGROUND

Irritable bowel syndrome (IBS) is a complex condition with multiple factors contributing to its aetiology and pathophysiology. Aetiologically these include genetics, life-time events and environment, and physiologically, changes in motility, central processing, visceral sensitivity, immunity, epithelial permeability and gastrointestinal microflora. Such complexity means there is currently no specific reliable biomarker for IBS, and thus IBS continues to be diagnosed and classified according to symptom based criteria, the Rome Criteria. Carefully phenotyping and characterisation of a 'large' pool of IBS patients across Europe and even the world however, might help identify sub-populations with accuracy and consistency. This will not only aid future research but improve tailoring of treatment and health care of IBS patients.

PURPOSE

The aim of this position paper is to discuss the requirements necessary to standardize the process of selecting and phenotyping IBS patients and how to organise the collection and storage of patient information/samples in such a large multi-centre pan European/global study. We include information on general demographics, gastrointestinal symptom assessment, psychological factors, quality of life, physiological evaluation, genetic/epigenetic and microbiota analysis, biopsy/blood sampling, together with discussion on the organisational, ethical and language issues associated with implementing such a study. The proposed approach and documents selected to be used in such a study was the result of a thoughtful and thorough four-year dialogue amongst experts associated with the European COST action BM1106 GENIEUR (www.GENIEUR.eu).

Abdominal bloating is the most bothersome symptom in irritable bowel syndrome with constipation (IBS-C): a large population-based Internet survey in Japan

Background

Abdominal bloating is a common symptom in patients with irritable bowel syndrome with constipation (IBS-C). However, it is not included among the required items in the Rome III diagnostic criteria for IBS. Little is known about an impact of abdominal bloating seen in patients with IBS-C. Using a large population-based sample, the aim of the present study was to investigate what is the most bothersome symptom in subjects with IBS-C.

Methods

An Internet survey of 30,000 adults drawn from the general public throughout Japan was conducted to identify subtypes of IBS using the Rome III diagnostic questionnaire. Consecutively, the screened subjects with IBS-C and the same number of age- and sex-matched non-IBS subjects who were randomly selected as controls were asked to answer a questionnaire on the degree of anxiety they experienced in their daily lives, thoughts about bowel habit, and their dominant gastrointestinal symptoms together with exacerbation factors (for IBS-C only).

Results

The screening survey showed that the prevalence of overall IBS was 16.5 % (female 17.4 %, male 15.5 %) and that 2.8 % met the criteria for IBS-C, 4.5 % for IBS with diarrhea (IBS-D) and 8.2 % for mixed IBS (IBS-M). Seven hundred and fifty-nine of 835 (90.9 %) subjects with IBS-C and 746 of 830 (89.9 %) control subjects completed the consecutive questionnaire. IBS-C subjects felt a higher degree of anxiety in their daily lives (p < 0.01) and considered bowel habit to be an indicator of health (p < 0.01) to a greater extent than control subjects. In IBS-C, the degree of anxiety was significantly associated with abdominal discomfort (p < 0.01), pain (p < 0.01) and bloating (p = 0.02), but not with the frequency of bowel habit (p > 0.1). Abdominal bloating was the most bothersome symptom (27.5 %), which was more likely to occur after a meal (52.2 %), at work/school (29.2 %) and during times of stress (26.8 %). Only 4.5 % of IBS-C subjects reported abdominal pain as the ‘most bothersome’ symptom.

Conclusions

A large population-based Internet survey suggests that abdominal bloating has a great impact on the daily lives of subjects diagnosed with IBS-C. Not only bowel movement/abdominal pain but also abdominal bloating should be evaluated in patients with IBS-C.

Electronic supplementary material

The online version of this article (doi:10.1186/s13030-016-0070-8) contains supplementary material, which is available to authorized users.

Bowel Disorders

Functional bowel disorders are highly prevalent disorders found worldwide. These disorders have the potential to affect all members of society, regardless of age, gender, race, creed, color or socioeconomic status. Improving our understanding of functional bowel disorders (FBD) is critical as they impose a negative economic impact to the global health care system in addition to reducing quality of life. Research in the basic and clinical sciences during the past decade has produced new information on the epidemiology, etiology, pathophysiology, diagnosis and treatment of FBDs. These important findings created a need to revise the Rome III criteria for FBDs, last published in 2006. This manuscript classifies the FBDs into five distinct categories: irritable bowel syndrome (IBS); functional constipation (FC); functional diarrhea (FDr); functional abdominal bloating/distention (FAB/D); and unspecified FBD (U-FBD). Also included in this article is a new sixth category, opioid induced constipation (OIC) which is distinct from the functional bowel disorders (FBDs). Each disorder will first be defined, followed by sections on epidemiology, rationale for changes from prior criteria, clinical evaluation, physiologic features, psychosocial features and treatment. It is the hope of this committee that this new information will assist both clinicians and researchers in the decade to come.

Lactulose Challenge Determines Visceral Sensitivity and Severity of Symptoms in Patients With Irritable Bowel Syndrome

BACKGROUND & AIMS

Patients with irritable bowel syndrome (IBS) can be assigned to groups with different gastrointestinal (GI) symptoms based on results from a combined nutrient and lactulose challenge. We aimed to identify factors that predict outcomes to this challenge and to determine whether this can be used in noninvasive assessment of visceral sensitivity in patients with IBS.

METHODS

We performed a prospective study of 100 patients with IBS diagnosed according to Rome III criteria (all subtypes) and seen at a secondary or tertiary care center. After an overnight fast, subjects were given a liquid breakfast (400 mL; Nutridrink) that contained 25 g lactulose. Before the challenge, we assessed visceral sensitivity (via rectal barostat), oro-anal transit time, and fecal microbiota composition (via 16S ribosomal RNA pyrosequencing); we determined IBS severity using questionnaires. The intensity of 8 GI symptoms, the level of digestive comfort, and the amount of exhaled H2 and CH4 in breath were measured before and during a 4-hour period after the liquid breakfast.

RESULTS

Based on the intensity of 8 GI symptoms and level of digestive comfort during the challenge, patients were assigned to groups with high-intensity GI symptoms (HGS; n = 39) or low-intensity GI symptoms (LGS; n = 61); patients with HGS had more severe IBS (P < .0001), higher somatization (P < .01), and lower quality of life (P < .05-.01) than patients with LGS. Patients with HGS also had significantly higher rectal sensitivity to random phasic distensions (P < .05-.001, compared with patients with LGS). There were no significant differences between groups in fecal microbiota composition, exhaled gas in breath, or oro-anal transit time.

CONCLUSIONS

We found, in a prospective study, that results from a lactulose challenge test could be used to determine visceral sensitivity and severity of IBS. The intensity of patient symptoms did not correlate with the composition of the fecal microbiota. The lactulose challenge test may help better characterize patients with IBS and evaluate the efficacy of new treatments. ClinicalTrial.gov no: NCT01252550.

Systematic review: instruments to assess abdominal pain in irritable bowel syndrome

BACKGROUND

Consensus on standard methods to assess chronic abdominal pain in patients with irritable bowel syndrome (IBS) is currently lacking.

AIM

To systematically review the literature with respect to instruments of measurement of chronic abdominal pain in IBS patients.

METHODS

Systematic literature search was performed in PubMed/Medline databases for studies using pain measurement instruments in patients with IBS.

RESULTS

One hundred and ten publications were reviewed. A multitude of different instruments is currently used to assess chronic abdominal pain in IBS patients. The single-item methods, e.g. the validated 10-point numeric rating scale (NRS), and questionnaires assessing gastrointestinal symptoms severity, focus mostly on the assessment of only the intensity of abdominal pain. Of these questionnaires, the validated IBS-Symptom Severity Scale includes the broadest measurement of pain-related aspects. General pain questionnaires and electronic momentary symptom assessment tools have been used to study abdominal pain in IBS patients, but have not yet been validated for this purpose. The evidence for the use of provocation tests, e.g. the rectal barostat with balloon distention, for measurement of abdominal pain in IBS is weak, due to the poor correlation between visceral pain thresholds assessed by provocation tests and abdominal pain as assessed by retrospective questionnaires.

CONCLUSIONS

The multitude of different instruments to measure chronic abdominal pain in IBS makes it difficult to compare endpoints of published studies. There is need for validated instruments to assess chronic abdominal pain in IBS patients, that overcome the limitations of the currently available methods.

Linaclotide in Chronic Idiopathic Constipation Patients with Moderate to Severe Abdominal Bloating: A Randomized, Controlled Trial

BACKGROUND

Abdominal bloating is a common and bothersome symptom of chronic idiopathic constipation. The objective of this trial was to evaluate the efficacy and safety of linaclotide in patients with chronic idiopathic constipation and concomitant moderate-to-severe abdominal bloating.

METHODS

This Phase 3b, randomized, double-blind, placebo-controlled clinical trial randomized patients to oral linaclotide (145 or 290 μg) or placebo once daily for 12 weeks. Eligible patients met Rome II criteria for chronic constipation upon entry with an average abdominal bloating score ≥5 (self-assessment: 0 10-point numerical rating scale) during the 14-day baseline period. Patients reported abdominal symptoms (including bloating) and bowel symptoms daily; adverse events were monitored. The primary responder endpoint required patients to have ≥3 complete spontaneous bowel movements/week with an increase of ≥1 from baseline, for ≥9 of 12 weeks. The primary endpoint compared linaclotide 145 μg vs. placebo.

RESULTS

The intent-to-treat population included 483 patients (mean age=47.3 years, female=91.5%, white=67.7%). The primary endpoint was met by 15.7% of linaclotide 145 μg patients vs. 7.6% of placebo patients (P<0.05). Both linaclotide doses significantly improved abdominal bloating vs. placebo (P<0.05 for all secondary endpoints, controlling for multiplicity). Approximately one-third of linaclotide patients (each group) had ≥50% mean decrease from baseline in abdominal bloating vs. 18% of placebo patients (P<0.01). Diarrhea was reported in 6% and 17% of linaclotide 145 and 290 μg patients, respectively, and 2% of placebo patients. AEs resulted in premature discontinuation of 5% and 9% of linaclotide 145 μg and 290 μg patients, respectively, and 6% of placebo patients.

CONCLUSIONS

Once-daily linaclotide (145 and 290 μg) significantly improved bowel and abdominal symptoms in chronic idiopathic constipation patients with moderate-to-severe baseline abdominal bloating; in particular, linaclotide significantly improved abdominal bloating compared to placebo, an important finding given the lack of agents available to treat abdominal bloating in chronic idiopathic constipation patients.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01642914.

Clinical presentation and pathophysiology of gastroparesis

Gastroparesis is a heterogeneous disorder defined by delay in gastric emptying. Symptoms of gastroparesis are nonspecific, including nausea, vomiting, early satiety, bloating, and/or abdominal pain. Normal gastric motor function and sensory function depend on a complex coordination between the enteric and central nervous system. This article discusses the pathophysiology of delayed gastric emptying and the symptoms of gastroparesis, including antropyloroduodenal dysmotility, impaired gastric accommodation, visceral hypersensitivity, and autonomic dysfunction. The underlying pathophysiology of gastroparesis is complex and multifactorial. The article discusses how a combination of these factors leads to symptoms of gastroparesis.

Prucalopride improves bowel function and colonic transit time in patients with chronic constipation: an integrated analysis

OBJECTIVES

Constipation is often characterized by slow colonic transit, but the relationship between colonic transit time (CTT) and symptoms is unclear. The aims of this study were to investigate the effect of prucalopride, a 5-hydroxytryptamine receptor-4 agonist, on CTT and assess the relationship between CTT and symptoms.

METHODS

This was an integrated analysis of three randomized, placebo-controlled, phase 2 dose-finding trials of prucalopride in patients with chronic constipation (ClinicalTrials.gov identifiers: NCT00617513; NCT00631813; and NCT00596596). Measurements of CTT were analyzed using radio-opaque markers at the start and end (4 or 12 weeks) of treatment. At these visits, patients assessed the presence and severity of their symptoms.

RESULTS

In total, 280 patients had CTT measurements before and at the end of treatment and were included in the analysis. Their mean age was 43 years, 93% were women, and mean duration of constipation was 19 years. After a once daily treatment with prucalopride 2 mg (n=98) and 4 mg (n=70), CTT was reduced by 12.0 h (95% confidence interval (CI): -18.9, -5.1) and 13.9 h (95% CI: -20.5, -7.4), respectively; CTT increased by 0.5 h (95% CI: -4.5, 5.5) with placebo (n=112). At the end of the trial, symptoms including bloating/flatulence/distension and straining were rated as severe or very severe by a higher proportion of patients with slow or very slow CTT (>48 h) than by those with normal CTT.

CONCLUSIONS

There was a clear relationship between increased CTT and increased symptom severity in patients with chronic constipation. Treatment with prucalopride accelerated CTT in these individuals.

Caecal pH is a biomarker of excessive colonic fermentation

AIM: To ascertain whether caecal pH is different in patients with irritable bowel syndrome (IBS), whose primary symptoms are bloating and distension, to healthy controls.

METHODS: Motility and pH data were reviewed from 16 patients with Rome III defined IBS and 16 healthy controls, who had undergone a wireless motility capsule (WMC) study using a standardized protocol. Motility measures were anchored around known anatomical landmarks as identified by compartmental pH changes. Sixty-minute epochs were used to quantify antral, duodenal, ileal, caecal and distal colonic contractility. The maximum and minimum pH was measured either side of the ileo-caecal junction.

RESULTS: No differences were seen in motility parameters, compartmental transit times or maximal ileal pH between the two groups. Caecal pH was significantly lower in patients compared to controls (5.12 ± 0.05 vs 6.16 ± 0.15, P < 0.0001). The ileal:caecal Δchange was greater in patients than controls (-2.63 ± 0.08 vs -1.42 ± 0.11, P < 0.0001). There was a significant correlation between caecal pH and right colonic contractility (r = 0.54, P = 0.002).

CONCLUSION: Patients with bloating and distension have a lower caecal pH compared to controls. The measurement of caecal pH using the WMC provides a quantifiable biomarker of fermentation potentially identifying those patients that may preferentially benefit from antibiotic or dietary interventions.

Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia

OBJECTIVE

Patients with irritable bowel syndrome and abdominal bloating exhibit abnormal responses of the abdominal wall to colonic gas loads. We hypothesised that in patients with postprandial bloating, ingestion of a meal triggers comparable abdominal wall dyssynergia. Our aim was to characterise abdominal accommodation to a meal in patients with postprandial bloating.

DESIGN

A test meal (0.8 kcal/ml nutrients plus 27 g/litre polyethylenglycol 4000) was administered at 50 ml/min as long as tolerated in 10 patients with postprandial bloating (fulfilling Rome III criteria for postprandial distress syndrome) and 12 healthy subjects, while electromyographic (EMG) responses of the anterior wall (upper and lower rectus, external and internal oblique via bipolar surface electrodes) and the diaphragm (via six ring electrodes over an oesophageal tube in the hiatus) were measured. Means +/- SD were calculated.

RESULTS

Healthy subjects tolerated a meal volume of 913±308 ml; normal abdominal wall accommodation to the meal consisted of diaphragmatic relaxation (EMG activity decreased by 15±6%) and a compensatory contraction (25±9% increase) of the upper abdominal wall muscles (upper rectus and external oblique), with no changes in the lower anterior muscles (lower rectus and internal oblique). Patients tolerated lower volume loads (604±310 ml; p=0.030 vs healthy subjects) and developed a paradoxical response, that is, diaphragmatic contraction (14±3% EMG increment; p<0.01 vs healthy subjects) and upper anterior wall relaxation (9±4% inhibition; p<0.01 vs healthy subjects).

CONCLUSIONS

In functional dyspepsia, postprandial abdominal distension is produced by an abnormal viscerosomatic response to meal ingestion that alters normal abdominal accommodation.

Abdominal bloating: pathophysiology and treatment

Abdominal bloating is a very common and troublesome symptom of all ages, but it has not been fully understood to date. Bloating is usually associated with functional gastrointestinal disorders or organic diseases, but it may also appear alone. The pathophysiology of bloating remains ambiguous, although some evidences support the potential mechanisms, including gut hypersensitivity, impaired gas handling, altered gut microbiota, and abnormal abdominal-phrenic reflexes. Owing to the insufficient understanding of these mechanisms, the available therapeutic options are limited. However, medical treatment with some prokinetics, rifaximin, lubiprostone and linaclotide could be considered in the treatment of bloating. In addition, dietary intervention is important in relieving symptom in patients with bloating.

Comorbidities in patients with irritable bowel syndrome with constipation or chronic idiopathic constipation: a review of the literature from the past decade

BACKGROUND

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are common functional bowel disorders. Patients with IBS-C or CIC often present with ≥ 1 comorbidity that coincides with either of these conditions. These comorbidities may make underappreciated contributions to the patient's overall disease burden.

OBJECTIVE

To identify the comorbidities that are the most frequently reported in patients with IBS-C or CIC in the medical literature.

METHODS

A literature search (January 2001-March 2012) was performed using the Medline and Medline In-Process databases. Studies of adult patients with IBS-C or CIC were selected, and the prevalence rates of the comorbidities were extracted and analyzed according to the body system affected.

RESULTS

A total of 70 distinct comorbidities were identified from 35 published studies. These comorbidities involved several body systems, including the gastrointestinal, genitourinary, psychiatric, endocrine, and allergic or immunologic systems. Functional dyspepsia and depression were the most common comorbidities in patients with IBS-C, whereas functional dyspepsia, diabetes, and depression were the most common comorbidities in patients with CIC.

CONCLUSION

Patients with IBS-C or CIC frequently experience a wide range of comorbidities that contribute to their disease burden. Thus, we believe that medical professionals should consider common comorbidities when diagnosing and treating patients with IBS-C or CIC.

Bloating and distention in irritable bowel syndrome: the role of gas production and visceral sensation after lactose ingestion in a population with lactase deficiency

OBJECTIVES

Bloating and distention are often attributed to dietary factors by patients with irritable bowel syndrome (IBS). This study examined the effects of gas production and visceral hypersensitivity on digestive symptoms after lactose ingestion in a population with lactase deficiency.

METHODS

IBS patients (n=277) and healthy controls (HCs, n=64) underwent a 20-g lactose hydrogen breath test (LHBT) with evaluation of hydrogen gas production and lactose intolerance (LI) symptoms. Abdominal distention (199 IBS, 40 HCs) was measured during LHBT. Rectal sensitivity (74 IBS, 64 HCs) was assessed by barostat studies.

RESULTS

Hydrogen production and distention were similar in IBS patients and HCs during LHBT; however, LI was more frequent in IBS (53.8 vs. 28.1%, P<0.001), especially bloating (39.0% vs. 14.1%, P<0.001) and borborygmi (39.0 vs. 21.9%, P=0.010). Only 59.0% of patients with bloating had distention. No correlation was observed between girth increment and bloating (P=0.585). IBS patients had lower rectal sensory thresholds (P=0.001). Multivariate analysis indicated that hydrogen production increased bloating (odds ratio (OR) 2.19, 95% confidence interval (CI) 1.09-4.39, P=0.028) and borborygmi (OR 12.37, 95% CI 3.34-45.83, P<0.001) but not distention (P=0.673). Visceral hypersensitivity was associated with bloating (OR 6.61, 95% CI 1.75-25.00, P=0.005) and total symptom score (OR 3.78, 95% CI 1.30-10.99, P=0.014).

CONCLUSIONS

Gas production and visceral hypersensitivity both contribute to digestive symptoms, especially bloating and borborygmi, in IBS patients after lactose ingestion. Objective abdominal distention is not correlated with subjective bloating.

Dietary sorbitol and mannitol: food content and distinct absorption patterns between healthy individuals and patients with irritable bowel syndrome

BACKGROUND

Sorbitol and mannitol are naturally-occurring polyol isomers. Although poor absorption and induction of gastrointestinal symptoms by sorbitol are known, the properties of mannitol are poorly described. We aimed to expand data on food composition of these polyols, and to compare their absorptive capacities and symptom induction in patients with irritable bowel syndrome (IBS) and healthy individuals.

METHODS

Food samples were analysed for sorbitol and mannitol content. The degree of absorption measured by breath hydrogen production and gastrointestinal symptoms (visual analogue scales) was evaluated in a randomised, double-blinded, placebo-controlled study in 21 healthy and 20 IBS subjects after challenges with 10 g of sorbitol, mannitol or glucose.

RESULTS

Certain fruits and sugar-free gum contained sorbitol, whereas mannitol content was higher in certain vegetables. Similar proportions of patients with IBS (40%) and healthy subjects (33%) completely absorbed sorbitol, although more so with IBS absorbed mannitol (80% versus 43%; P = 0.02). Breath hydrogen production was similar in both groups after lactulose but was reduced in patients with IBS after both polyols. No difference in mean (SEM) hydrogen production was found in healthy controls after sorbitol [area-under-the-curve: 2766 (591) ppm 4 h(-1) ] or mannitol [2062 (468) ppm 4 h(-1) ] but, in patients with IBS, this was greater after sorbitol [1136 (204) ppm 4 h(-1) ] than mannitol [404 (154) ppm 4 h(-1) ; P = 0.002]. Overall gastrointestinal symptoms increased significantly after both polyols in patients with IBS only, although they were independent of malabsorption of either of the polyols.

CONCLUSIONS

Increased and discordant absorption of mannitol and sorbitol occurs in patients with IBS compared to that in healthy controls. Polyols induced gastrointestinal symptoms in patients with IBS independently of their absorptive patterns, suggesting that the dietary restriction of polyols may be efficacious.

A combined nutrient and lactulose challenge test allows symptom-based clustering of patients with irritable bowel syndrome

OBJECTIVES

The aim of the present pilot study was to evaluate the usefulness of a test meal containing lactulose in the non-invasive assessment of visceral sensitivity in irritable bowel syndrome (IBS), and to identify subsets of IBS patients based on gastrointestinal (GI) symptom generation.

METHODS

We included 43 patients with IBS (Rome III) and 29 healthy controls. The fasted subjects were served three test meals consisting of a 400-ml liquid breakfast alone or containing lactulose (15 or 25 g) in a double-blind crossover design. Seven GI symptoms, overall digestive comfort, and exhaled H2/CH4 were assessed at baseline and every 15 min during 4 h after meal intake. Anxiety and depression were assessed only at baseline. A mapping of the seven GI symptoms was done using a Principal Component Analysis (4 h mean area under the curve, AUC). Independently, a hierarchical cluster analysis was performed on the same parameters to identify GI symptom-based IBS clusters.

RESULTS

All three tests were well tolerated. The 25 g lactulose challenge enabled discrimination of IBS from healthy controls according to the symptom response. This challenge also enabled clustering of IBS subjects in two subgroups based mainly on bloating, distension, and discomfort symptoms (2,457 (2,043-2,872), 2,450 (1,910-2,990), 2,602 (2,126-3,079) vs. 537 (383-691), 619 (458-780), 643 (432-854); 4 h mean AUC; P<0.0001), overall digestive comfort (1807 (1318-2295) vs. 3350 (2942-3758); 4 h mean AUC; P<0.0001), and anxiety at baseline (9.2 (7.0-11.5) vs. 5.5 (4.2-6.9); Hospital Anxiety and Depression scale anxiety mean scores; P=0.003). This clustering was independent of the Rome III subtype and the amount of exhaled H2/CH4.

CONCLUSIONS

The lactulose challenge test seems to be a promising tool to assess visceral sensitivity in IBS, and to subgroup IBS patients based on their symptom pattern.

Rectal hyposensitivity

Impaired or blunted rectal sensation, termed rectal hyposensitivity (RH), which is defined clinically as elevated sensory thresholds to rectal balloon distension, is associated with disorders of hindgut function, characterised primarily by symptoms of constipation and fecal incontinence. However, its role in symptom generation and the pathogenetic mechanisms underlying the sensory dysfunction remain incompletely understood, although there is evidence that RH may be due to 'primary' disruption of the afferent pathway, 'secondary' to abnormal rectal biomechanics, or to both. Nevertheless, correction of RH by various interventions (behavioural, neuromodulation, surgical) is associated with, and may be responsible for, symptomatic improvement. This review provides a contemporary overview of RH, focusing on diagnosis, clinical associations, pathophysiology, and treatment paradigms.

Rectal hypersensitivity as hallmark for irritable bowel syndrome: defining the optimal cutoff

BACKGROUND

Visceral hypersensitivity is a frequently observed hallmark of irritable bowel syndrome (IBS). Studies have reported differently about the presence of visceral hypersensitivity in IBS resulting from lack of standardization of the barostat procedure and due to different criteria used to assess hypersensitivity. We aimed to calculate the optimal cutoff to detect visceral hypersensitivity in IBS.

METHODS

A total of 126 IBS patients and 30 healthy controls (HC) were included for assessment of visceroperception by barostat. Pain perception was assessed on a visual analogue scale (VAS). ROC-curves were used to calculate optimal discriminative cutoff (pressure and VAS-score) between IBS patients and HC to define hypersensitivity. Furthermore, pain perception to distension sequences below the pressure threshold for hypersensitivity was defined as allodynia.

KEY RESULTS

Irritable bowel syndrome patients showed increased visceroperception compared to HC. Thresholds for first sensation and first pain were lower in IBS patients VS HC (P < 0.01). ROC-curves showed optimal discrimination between IBS patients and HC at 26 mmHg with a VAS cutoff ≥20 mm. Using this criterion, hypersensitivity percentages were 63.5% and 6.6% in IBS patients and HC, respectively. No significant differences were observed between IBS subtypes. Allodynia was found in a small number of patients (11%).

CONCLUSIONS & INFERENCES

Optimal cutoff for visceral hypersensitivity was found at pressure 26 mmHg with a VAS ≥20 mm, resulting in 63.5% of IBS patients being hypersensitive and 11% being allodynic. Standardization of barostat procedures and defining optimal cutoff values for hypersensitivity is warranted when employing rectal barostat measurements for research or clinical purposes.

Functional abdominal bloating with distention

Ten to 25% of healthy persons experience bloating. It is particularly common in persons with the irritable bowel syndrome and constipation. While the cause of bloating remains unknown old explanations such as a excessive intestinal gas, exaggerated lumbar lordosis and psychiatric problems have been disproved. New suggestions include recent weight gain, weak or inappropriately relaxed abdominal muscles, an inappropriately contracted diaphragm and retained fluid in loops of distal small bowel. No treatment is of unequivocal benefit but a low FODMAPs diet, probiotics and the non-absorbable antibiotic rifaximin offer some hope. Treatment by weight loss, abdominal exercise, prokinetics and girdles need more study.

Intestinal microbiota, pathophysiology and translation to probiotic use in patients with irritable bowel syndrome

Probiotic agents have received growing attention in recent years as an alternative therapeutic tool in the management of irritable bowel syndrome. In this article, we will discuss the rationale that support this indication, including the role of intestinal microbiota in gastrointestinal function in both human and animal models, potential links between an impaired microbiota imbalance and the psycho-immunopathophysiology of irritable bowel syndrome, and the results of the available clinical trials to date.

Altered temporal characteristics of the rectoanal inhibitory reflex in patients with abdominal distension

The rectoanal inhibitory reflex (RAIR) is important in gas and stool evacuation. We examined RAIR features in patients with chronic constipation who exhibited bloating with and without abdominal distension, to determine whether alterations in RAIR may be a factor in the pathogenesis of abdominal distension. Seventy-five female patients with chronic constipation with or without abdominal distension were included in the study. The presence or absence of abdominal distension was assessed according to the Rome II questionnaire. All patients underwent both RAIR and rectal sensitivity testing, and specific RAIR parameters were analyzed. Patients were divided into two groups: abdominal bloating with distension (D, n = 55) and abdominal bloating without distension (ND, n = 20). D had a longer time to the onset of anal sphincter inhibition (latency of inhibition) (P = 0.03) compared with ND. In logistic regression analysis, a combination of age, latency of inhibition and the time measured from onset of inhibition to the point of maximum inhibition predicted abdominal distension (P = 0.002). There were no differences between groups for the time from point of maximum inhibition to recovery and for the percentage of internal anal sphincter relaxation. This is the first study to examine the role of RAIR in patients with abdominal distension. Female patients with constipation and abdominal distension exhibited differences in the temporal characteristics of, but not in the degree of, anal sphincter relaxation compared with patients without distension. Since this study was uncontrolled, further studies are necessary to determine the contribution of altered anorectal reflexes to abdominal distension.

Unraveling functional abdominal bloating and distension: the role of thoraco-abdominal accommodation and a physical sign to aid its detection

Bloating and distension are common complaints in patients with irritable bowel syndrome of which the cause has remained elusive, although it has been shown that the obvious explanation of excessive gas is unlikely. The recent application of technologies such as the gas challenge technique, abdominal inductance plethysmography, CT scanning, as well as electromyography of the diaphragm and anterior abdominal wall, have allowed the situation to be slowly unraveled. It is now seems probable that the pathophysiology of bloating and distension are subtly different with the former having a sensory component whereas mechanical factors, such as disordered abdominal accommodation, contribute more to the latter.

Abdominal bloating and distension: what is the role of the microbiota

Most patients with irritable bowel syndrome complain of a sensation of an increase in pressure within their abdomen during the course of the day which is called bloating and, in approximately half of these individuals, this symptom is accompanied by an actual increase in abdominal girth, which is referred to as distension. The pathophysiology of these two phenomena is somewhat different and it is now recognised that a whole variety of overlapping mechanisms are involved. Some of these are potentially amenable to treatment by modification of the bacterial flora of the gut and this article reviews the evidence for this.